Typically, a solid oxide fuel cell (SOFC) employs an electrolyte of ion-conductive solid oxide such as stabilized zirconia. The electrolyte is interposed between an anode and a cathode to form an electrolyte electrode assembly (MEA). The electrolyte electrode assembly is interposed between separators (bipolar plates). In use, generally, predetermined numbers of the electrolyte electrode assemblies and the separators are stacked together to form a fuel cell stack.
In the fuel cell of this type, Japanese Laid-Open Patent Publication No. 2004-235060 discloses a fuel cell having an object of achieving the uniform gas flow distribution of the air and fuel supplied to the cells, and uniform distribution of the heat or stress generated in the cells.
In the conventional technique, as shown in FIG. 18, a cell forming plate 1a is provided. At the axial center of a solid electrolyte substrate 2a, a ring shaped member 4a having a central through hole 3a is provided. A gas channel 6a having a plurality of peripheral through holes 5a around the central through holes 3a is formed. According to the disclosure, in the structure, the temperature difference between the outer circumferential region and the central region of the cell is reduced, and the heat stress in the overall cell can be reduced.
Further, in a solid oxide fuel cell disclosed in Japanese Laid-Open Patent Publication No. 2006-302749, as shown in FIG. 19, a porous current collector 3b is provided in a space formed between the separators 1b, 2b. Gases are supplied into, and discharged from the space through gas inlet holes 4b, 5b and gas discharge holes 6b, 7b. The gas inlet hole 4b and gas discharge hole 6b are formed in the separator 1b, and the gas inlet hole 5b and gas discharge hole 7b are formed in the separator 2b. In the porous current collector 3b, a compression band 8b is provided, and the compression band 8b is joined to the separator 2b. 
According to the disclosure, in the structure, reduction in the thickness of the separator, and improvement in the strength of the separator are achieved, and positional deviation of the porous current collector from the separator due to vibration or impact can be prevented.
Further, in Japanese Laid-Open Patent Publication No. 2004-235060, since each cell forming plate 1a comprises one electrolyte electrode assembly, if any power generation failure occurs in one of the power generation cells, the failure causes malfunction in power generation of the entire fuel cell. Therefore, power generation cannot be performed efficiently.
Further, since the cell forming plate 1a has a ring shape having the central through hole 3a, the electrolyte electrode assembly also has a ring shape. Therefore, the electrolyte electrode assembly tends to be damaged or cracked easily. Further, it is not possible to suppress radiation of heat generated in the power generation, and heat efficiency is lowered.
Further, in the case of applying the load to the cells in the stacking direction by putting a priority on the sealing performance, the load is directly applied to the electrolyte electrode assembly. By the excessive load applied to the electrolyte electrode assembly, the electrolyte electrode assembly may be damaged or cracked undesirably.
Further, in Japanese Laid-Open Patent Publication No. 2006-302749, one electrolyte electrode assembly is sandwiched between the separators 1b, 2b. In the structure, if any power generation failure occurs in one of the power generation cells, the failure causes malfunction in power generation of the entire fuel cell. Therefore, power generation cannot be performed efficiently.
Further, the electrolyte electrode assembly has a ring shape, and thus, the electrolyte electrode assembly tends to be damaged or cracked easily. Further, it is not possible to suppress radiation of heat generated in the power generation, and heat efficiency is lowered.
Further, in the case of applying the load to the cells in the stacking direction by putting a priority on the sealing performance, the load is directly applied to the electrolyte electrode assembly. By the excessive load applied to the electrolyte electrode assembly, the electrolyte electrode assembly may be damaged or cracked undesirably.